The invention relates to a laminated rotor assembly that is particularly useful in the manufacture of dynamoelectric machines employing cast conductors and, more particularly, it relates to such an assembly that requires only two differently configured sets of rotor laminations to form a rotor having radial cooling ducts that are connected to axial coolant passageways in a manner that enables rotor conductors to be efficiently cooled. The invention also makes it possible to cast the conductors of a rotor assembly without requiring the use of spacer pins, or spot welded collar subassemblies, separately inserted into the laminae assembly of the rotor during a casting operation to prevent the flow of casting metal from the conductor slots into cooling ducts of the assembly.
Before the present invention, the use of axial and radial cooling passageways through the rotors of electric motors and generators was well known. It was common practice in the manufacture of large-diameter dynamoelectric machines to cast conductors in their laminated rotor assemblies by utilizing various types of spacers to prevent the molten casting metal from entering the rotor air ducts during a casting operation. For example, U.S. Pat. No. 2,368,296 discloses a method of forming radial ventilating passages in a cast rotor in which ring-shaped spacers are inserted between groups of laminations during the casting operation. The same inventor named in the foregoing patent discloses in U.S. Pat. No. 2,368,295 the use of cardboard or similar combustible material to form spacers in a rotor made of stacked laminations so that during a casting operation the combustible material blocks the casting metal from the coolant passageways. Similarly, in U.S. Pat. No. 2,607,968 there is described a method for casting dynamoelectric machine rotors so that air ducts are formed by spacers made of frangible plaster material that is positioned between the groups of the laminations in the rotor during a casting operation. Following the casting procedure, the plaster material is disintegrated and washed from the air ducts.
Although the use of such dissolvable or frangible spacer materials is well-known, it is also a common practice in the manufacture of relatively large dynamoelectric machine rotors to place a plurality iof removable steel pins, or spot welded collar subassemblies, between sections of the rotor laminations to form the desired cooling ducts in the rotors. The use of such a reusable spacer procedure is shown, for example, in U.S. Pat. No. 2,504,824.
Well before the development and commercialization of such removable ring or pin techniques for casting conductors in laminated rotors, it was known to fabricate laminated rotors of a series of differently configured punched laminations arranged to form axial coolant passageways connected to radial coolant ducts by venting channels. An example of several early configurations of that type of ventilating arrangement in a wound rotor structure is shown in U.S. Pat. No. 890,577 which issued on June 9, 1908. However, since such early rotor cooling arrangements were not suitable for use in manufacturing cast conductor rotors, due to the fact that they would allow molten conductor metal to enter the coolant passageways therein, it remained common practice to manufacture rotors having cast conductors by the aforementioned movable spacer-pin methods.
In more recent times, as shown in U.S. Pat. No. 3,684,906, which issued on Aug. 15, 1972 to the applicant named herein, a relatively small castable rotor for refrigerant compressor motors was disclosed in which a plurality of sets of differently configured rotor laminae were arranged to form tortuous paths through the rotor from accurately spaced axial refrigerant-carrying passageways, through intermediate vent passageways, to arcuately disposed radial ducts. Such small refrigerant compressor motors are distinguished from the present invention by requiring the use of radial coolant ducts in two different sets of laminations so that the radial ducts in either such set do not extend the full depth of the adjacent conductor slots. Furthermore, the flow-restricting nature of the small, tortuous ducts used to carry refrigerant through such rotors are not suitable for use as coolant passageways for larger air-cooled rotors in which large volumes of air must be moved through the rotor ducts with little pressure loss.
Finally, in two co-pending U.S. patent applications; Ser. No. 824,104, filed Aug. 12, 1977, now U.S. Pat. No. 4,301,386 and Ser. No. 95,024, filed Nov. 16, 1979, now U.S. Pat. No. 4,286,182 both of which are assigned to General Electric Co., the present applicant has disclosed laminated rotor assemblies for rotors of dynamoelectric machines which assemblies use three or more differently configured sets of rotor laminations to provide coolant vent passageways axially and radially through rotors that can be formed with cast conductors, without requiring use of casting pins, removable plugs, or other prior art means, such as those discussed above, to block molten casting metal from the coolant passageways. The present invention is an improvement over the invention disclosed in those two co-pending applications because it avoids the expense and manufacturing complexity inherent in using more than two differently configured sets of rotor laminations, when the diameter of a rotor is sufficiently large to enable effective use of this improvement invention.